Home made 3 phase converter?

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Electron_Sam78

Electron_Sam78

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Location
Palm Bay, FL
I had a guy ask me about problems he's having with his home made 3 phase converter. I told him I couldn't help him since I've never even heard of such a thing let alone had any experience with something like that. Apparently he has a 10HP 3 motor he's trying to run but only has single phase power source. In order to get the 3 phase power he has another 3 phase motor hooked up with two hot legs and then gets it running by using another single phase motor to turn the shaft. Then he's expecting the unused leg of the 3 phase motor to magically produce the third phase so he can tap into that along with the 2 phases from the source to run his 3 phase, 10 HP motor. But it's not and he's tripping a 50 amp breaker!

Have any of you ever heard of anything like this? What the crap? I know motors don't work like generators. I guess he got this idea from the Internet and there are apparently sites telling you how to do it but they all conflict each other (suprisingly) :confused:
 
I

IMM_Doctor

Senior Member
I have personally seen one of these DIY phase converters in action. The one I witnessed had a single-phase motor driving a three-phase motor via belt. The 240 v single phase started the single phase motor, and then a short duration timer turned on a contactor that applied 240v single phase to 2 legs of the driven 3-phase motor. The 3rd phase is generated, and can be used to drive 3phase motors down-stream.

It was years ago, so after I read your post, I Google it. It looks like there is an alternate way that does not require the single phase motor to start, and establish rotation, but using a capacitor and and timer. This seems to be more efficient.

I would stay on the Google-train, and try to find documenation that matches your installation to aid in de-bugging.
 
Fulthrotl

Fulthrotl

~Autocorrect is My Worst Enema.~
Location
HB, CA (19 Hrs. 22 Min. from Winged Horses)
Occupation
E
Electron_Sam78 said:
I had a guy ask me about problems he's having with his home made 3 phase converter. I told him I couldn't help him since I've never even heard of such a thing let alone had any experience with something like that. Apparently he has a 10HP 3 motor he's trying to run but only has single phase power source. In order to get the 3 phase power he has another 3 phase motor hooked up with two hot legs and then gets it running by using another single phase motor to turn the shaft. Then he's expecting the unused leg of the 3 phase motor to magically produce the third phase so he can tap into that along with the 2 phases from the source to run his 3 phase, 10 HP motor. But it's not and he's tripping a 50 amp breaker!

Have any of you ever heard of anything like this? What the crap? I know motors don't work like generators. I guess he got this idea from the Internet and there are apparently sites telling you how to do it but they all conflict each other (suprisingly) :confused:
Click to expand...

yeah, it'll work. i've seen them... the problem with a homemade one is you
have to use a much larger motor than the load motor, like a 10 horse motor
to generate for a 3 horse motor.... the one i saw homebuilt, the guy used
a old style pull rope hub from a lawnmower... the kind you wrapped with
4' of rope and pulled.... he'd hit the switch, and give a yank, and off it'd
go, single phasing.... and then he'd start the milling machine....

i've got a 3 hp roto phase sitting in my garage, brand new, unused... looks
like a motor with no output shaft, and a large peckerhead... they list new
for about $600.... he can always go buy a real one if all else fails.....

there's us made ones, and chinese made ones... and the chinese made ones
always seemed to smoke..... i'd avoid the solid state ones... i've seen two
of those actually catch fire.... :smile:


randy
 
mxslick

mxslick

Senior Member
Location
SE Idaho
Fulthrotl said:
<snip> there's us made ones, and chinese made ones... and the chinese made ones
always seemed to smoke..... i'd avoid the solid state ones... i've seen two
of those actually catch fire.... :smile:


randy
Click to expand...
Bold added by me..

Really? Which brands of solid state caught fire? Was it in an application with several starts per hour? One that I had (and sold on fleabay) did contain a warning limiting the number of starts per hour.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
George, are you not aware of what a VFD (Variable Frequency Drive) is? The 120v 1ph is converted to 480v 3ph by the VFD. Think of it as a solid-state motor-generator.

It's not free energy, mind you. The Kva must still be supplied. The current needed at 120v 1ph is much greater than the 480v 3ph current delivered.
 
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